This invention concerns an electromagnetic induction method and apparatus therefor for simultaneously collapsing and propelling a workpiece; and, more particularly, it relates to an improved electromagnetic induction method and an improved apparatus for carrying out the method for progressively collapsing a relatively lightweight workpiece of annular shape and sheetlike construction toward an axis of the apparatus while at the same time accelerating and propelling the collapsed workpiece at a relatively high velocity in a direction outwardly of the apparatus and along the axis thereof.
In the past, various techniques have been developed for electromagnetically deforming a workpiece, propelling a workpiece or a combination thereof. For example, U.S. Pat. No. 3,295,412 to Morley et al. concerns a metallic particle accelerometer. The apparatus is generally made up of a magnetically responsive and deformable armature 14 and a cone-shaped solid explosive 30 operatively associated therewith. When the explosive is ignited, the armature is deformed to a conical shape. During ignition of the explosive a pulse coil is energized to accelerate and propel both the deformed armature and the particle carried thereby. U.S. Pat. No. 3,318,127 to Astleford, Jr. concerns an apparatus for magnetically forming a workpiece. The apparatus is generally made up of a pulse coil, a power supply control circuit; and a helically configured, field-shaping element. This shaping element assists in concentrating the magnetic flux uniformly about a workpiece to be formed. A technical report, that is entitled "Single Stage Pulsed Induction Reaction Engine" by Peter Mongeau under U.S. Army contract DAAK 10-79-C-0384 with the Francis Bitter National Magnet Laboratory of the Massachusetts Institute of Technology, relates to an apparatus for accelerating and propelling a ring-shaped workpiece without deforming the workpiece. The apparatus is generally comprised of a power supply circuit and a magnetic multi-ring flat-shaped pulse coil for accelerating and propelling the workpiece when the coil is energized. An article, that is entitled "Smart Munition System Developed for DARPA" as reported in the publication of "Aviation Week and Space Technology" of Sept. 22, 1982, discloses a dense metal disk. The disk, after being launched from a parent missile or rocket-type vehicle during flight of the vehicle, is explosively shaped into a slug-shaped configuration that has armor penetrating characteristics. None of the aforediscussed articles, report or references remotely suggest an improved electromagnetic induction apparatus and method for progressively collapsing an annular workpiece to form an approximately slug-shaped workpiece of solid, rigid construction while at the same time the progressively collapsed workpiece is accelerated and propelled at a relatively high velocity in a direction outwardly of the apparatus and along an axis thereof.